Covalent bonding synthesis of magnetic graphene oxide nanocomposites for Cr(III) removal

Abstract

A covalent bonding technique to obtain magnetic graphene oxide nanocomposites (Fe₃O₄/SiO₂–GO) decorated with core/shell nanoparticles is reported. Fe₃O₄/SiO₂–GO was characterized by transmission electron microscopy, energy dispersive X-ray spectrometer, X-ray diffraction, Fourier transform infrared, Raman, and thermogravimetric analysis techniques. Through covalent synthesis method, magnetic core/shell particles in size of 20–40 nm were homogeneously dispersed onto graphene oxide. The characteristic Si–O–Si peak (1091, 468 cm⁻¹), Fe–O (576 cm⁻¹), and aromatic C=C (1621 cm⁻¹) were the direct evidences to consolidate the formation of the Fe₃O₄/SiO₂–GO. The DTG curve showed about 54.45 wt% of metal oxide deposited on the surface of GO. The adsorption behaviors, including adsorption kinetics and isotherms parameters, effect factors, and mechanisms of chromium adsorption on Fe₃O₄/SiO₂–GO were studied. Fe₃O₄/SiO₂–GO demonstrated an extremely fast Cr(III) removal from the wastewater within 5 min and could be separated faster by using a permanent magnet. The adsorption kinetics followed the pseudo-second-order model and Fe₃O₄/SiO₂–GO exhibited better Cr(III) removal efficiency in solutions with high pH (>3). The adsorption of Cr(III) fits the Freundlich equation well. Based on abundant oxygen functional groups and negative surface charge on Fe₃O₄/SiO₂–GO, the adsorption mechanisms could be explained as electrostatic interactions and ion exchange. The significantly reduced treatment time required to remove the Cr(III) and the applicability in treating the solutions with high pH made Fe₃O₄/SiO₂–GO promise for the efficient removal of heavy metals from the leather industry wastewater.

Keywords:

• Graphene oxide
• Fe₃O₄/SiO₂–GO
• Covalent synthesis
• Adsorption
• Cr(III) removal

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Covalent bonding synthesis of magnetic graphene oxide nanocomposites for Cr(III) removal

Acknowledgments

This work was financially supported by State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (Grant No. 2010DX06), National Natural Science Foundation of China (No. 51178136), and State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (No. MARC2012D009).